The present invention is directed, in general, to wireless network and, more specifically, to a system for ensuring backward compatibility in radio link protocol versions.
The high level of competition in wireless communication equipment has driven the price of cellular service down to the point where it is affordable to a large segment of the population. Wireless subscribers use a wide variety of wireless devices, including cellular phones, personal communication services (PCS) devices, and wireless modem-equipped personal computer (PCs), among others. The large number of subscribers and the many applications for wireless communications have created a heavy subscriber demand for radio frequency (RF) bandwidth. To meet this demand, wireless service providers have maximized frequency by making individual cell sites smaller and using a greater number of cell sites to cover the same geographical area. Additionally, just as increased modem speeds made widespread use of the Internet possible and more popular, wireless communication protocols and standards are constantly improved in order to increase data bit rates over the wireless link between a wireless communication-device (or mobile station) used by a subscriber and a base station of a wireless network. For example, third generation (3G) wireless devices are expected to transmit data in excess of 140 kilobits per second (kbps) in the forward channel (i.e., from base station to mobile station) and in the reverse channel (i.e., from mobile station to base station).
To support the higher data rates, it is necessary to improve the radio link protocol (RLP) used by base stations and mobile stations to synchronize the transmission of data in the forward and reverse channels. As is well known, base stations and mobile stations communicate in a number of control channels and traffic channels. The control channels, namely pilot, synchronization (sync), paging, and access, are used to register a mobile station with a wireless network and to set up a call in a data traffic channel. The data traffic channels are used to transport subscriber voice and/or data signals.
Within a traffic channel, the radio link protocol (RLP) is used to synchronize the transmission of frames of data in the forward and reverse channels. Previous versions of RLP, such as RLP2 and RLP3 supported data bit rates up to 14.4 Kbps. RLP4 is intended to support much higher bit rates and different frames sizes.
Unfortunately, the control channels of conventional wireless. networks do not provide a mechanism that allows a mobile station and a base station to agree upon a particular RLP version prior to the setup of a traffic channel. This leads to compatibility problems if a base station attempts to transmit traffic data in RLP4 to a base station that only supports RLP1, RLP2 or RLP3.
There is therefore a need in the art for wireless systems that provide backward compatibility between different versions of the radio link protocol in a wireless network. More particularly, there is a need for an improved wireless network base station that is capable of determining the radio link protocol of a mobile station and adjusting the radio link protocol used by the base station to match the radio link protocol of the mobile station.
To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to provide, for use in a wireless network comprising a plurality of base stations capable of communicating with a plurality of mobile stations, a system capable of controlling the transmission of data in a traffic channel between a first one of the plurality of base stations and a first one of the mobile stations. In an advantageous embodiment of the present invention, the system comprises: 1) a radio link protocol (RLP) controller capable of causing the first base station to transmit to the first mobile station a first data transfer control message according to a first radio link protocol version; and 2) a timer coupled to the RLP controller capable of providing the RLP controller an elapsed time after the transmission of the first data transfer control message, wherein the RLP controller, in response to a determination that an acknowledgment message has not been received from the mobile station before the elapsed time has exceeded a maximum value, transmits to the first mobile station a second data transfer control message according to a second radio link protocol version.
According to one embodiment of the present invention, the first data transfer control message is a first control frame.
According to another embodiment of the present invention, the control frame comprises a first synchronization (SYNC) frame having a control field set to a SYNC value associated with the first radio link protocol version.
According to still another embodiment of the present invention, the second data transfer control message is a second control frame.
According to yet another embodiment of the present invention, the control frame comprises a second synchronization (SYNC) frame having a control field set to a SYNC value associated with the second radio link protocol version.
According to a further embodiment of the present invention, the maximum value is adjustable.
According to a further embodiment of the present invention, the RLP controller transmits the first data transfer control message to synchronize a transmission of data frames to the mobile station and wherein the RLP controller, upon determining that synchronization has been lost with the mobile station, transmits a different data transfer control message to re-synchronize a transmission of data frames to the mobile station.
According to a further embodiment of the present invention, a sequence number length associated with the different data transfer control message is different than a sequence number length associated with the first data transfer control message.
The foregoing has outlined rather broadly the features and technical advantages of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they may readily use the conception and the specific embodiment disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.
Before undertaking the DETAILED DESCRIPTION, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms xe2x80x9cincludexe2x80x9d and xe2x80x9ccomprise,xe2x80x9d as well as derivatives thereof, mean inclusion without limitation; the term xe2x80x9cor,xe2x80x9d is inclusive, meaning and/or; the phrases xe2x80x9cassociated withxe2x80x9d and xe2x80x9cassociated therewith,xe2x80x9d as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term xe2x80x9ccontrollerxe2x80x9d means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.